1. Field of the Invention
The invention relates to a rolling bearing.
2. Description of the Related Art
Many rolling bearings are used for various types of industrial equipment. A rolling bearing includes an inner ring, an outer ring, a plurality of rolling elements, and a cage. The rolling elements are interposed between the inner ring and the outer ring. The cage holds the rolling elements. For example, in each rolling bearing 90 that supports a rotating shaft 95 in a housing 97, an inner ring 91 is fitted over and attached to the rotating shaft 95, and an outer ring 92 is attached to an inner peripheral surface 98 of the housing 97, as depicted in FIG. 6.
In particular, when the rolling bearing 90 is a deep groove ball bearing and is subjected to an axial load in one direction, the inner ring 91 and the rotating shaft 95 are assembled in a “interference fit” state. In contrast, the outer ring 92 and the housing 97 are often assembled in a “clearance fit” state. Thus, in a use state where the rotating shaft 95 is rotating, creep (slip of the outer ring 92 with respect to the housing 97 in a circumferential direction) is likely to occur between the outer ring 92 and the housing 97.
Thus, a rolling bearing has been proposed in which a groove (annular groove) is formed in an outer peripheral surface of the outer ring 92 to suppress possible creep (see Japanese Patent Application Publication No. 2006-322579 (JP 2006-322579 A) or Japanese Patent Application Publication No. H10-37967 (JP H10-37967 A)). This rolling bearing enables suppression of creep that is likely to occur when a heavy load is imposed on the bearing in a radial direction. The creep that is likely to occur when such a load is imposed on the bearing causes the outer ring 92 to slip slowly in the same direction as a rotating direction of the bearing.
As described above, the annular groove 93 formed in the outer peripheral surface of the outer ring 92 enables the creep as described above to be suppressed. However, in this case, the contact area between the outer peripheral surface of the outer ring 92 and the housing 97 is reduced to increase a contact surface pressure on the housing 97. In particular, the housing 97 is brought into contact with a portion 99 in which side surfaces of the annular groove 93 cross at right angles outer peripheral surfaces of cylindrical portions 94 located on the opposite sides of the annular groove 93. This locally increases the surface pressure, and even slight creep of the outer ring 92 makes wear of the housing 97 likely to progress.
In the rolling bearing described in JP H10-37967 A, the annular groove 93 formed in the outer peripheral surface of the outer ring 92 is shaped like a circular ring as depicted in a sectional view in FIG. 7. In this case, compared to the case in JP 2006-322579 A, even when the housing 97 is brought into contact with the portion 99 in which the annular groove 93 crosses the outer peripheral surfaces of the cylindrical portions 94, the contact surface pressure on the housing 97 is less likely to increase.
However, the annular groove 93 having a circular-arc sectional shape makes dimensional management and production management during a manufacturing process for the outer ring 92 slightly difficult. That is, the annular groove 93 is formed, as depicted in FIG. 8A, by moving a grinding wheel 96 closer to the outer peripheral surface of the outer ring 92 and further bringing the grinding wheel 96 into contact with the outer peripheral surface as depicted by a long dashed double-short dashed line. However, when a cutting depth E1 of the grinding wheel 96 with respect to the outer ring 92 is even slightly larger than a set value E0 (see FIG. 8A) as depicted in FIG. 8B, a groove width X1 of the annular groove 93 formed is excessively larger than a specified groove width X0 (see FIG. 8A). In contrast, when a cutting depth E2 of the grinding wheel 96 is even slightly smaller than the set value E0 (FIG. 8A) as depicted in FIG. 8C, a groove width X2 of the annular groove 93 formed is excessively smaller than the specified groove width X0 (FIG. 8A). In other words, when the cutting depth E0 of the grinding wheel 96 varies (E1, E2), the dimension of the groove width (X1, X2) of the annular groove 93 is significantly affected, making dimensional management and production management difficult.
The dimensional management of the groove width X0 of the annular groove 93 is important. A reduced groove width X2 as depicted in FIG. 8C degrades the creep suppression effect of the annular groove 93. On the other hand, an excessively large groove width X1 as depicted in FIG. 8B narrows the outer peripheral surfaces of the cylindrical portions 94 to increase the contact surface pressure between the outer peripheral surfaces and the housing 97. This may cause wear.